Let me rephrase my question. What does a waterstone do better than ceramic or diamond stones?
I know some things that waterstones do differently than those two. There are probably more, but here's my list:
DMT versus waterstones: Waterstones come in a wider variety of grit sizes, so you've got more choices, including going to much higher polish level than DMTs or Atomas or any other diamond plate I'm aware of. Probably more importantly though is the difference in the abrasive that does the cutting. Diamonds cut like crazy! But they cut with a particle that is very pointy and doesn't break off. So, as far as I can tell, diamonds tend to leave a rougher finish than other abrasives at the same particle size (micron size). The finish from a coarse DMT is going to be rougher looking than the finish from a typical 1000 grit waterstone. You'd expect them to be the same based on particle size, but they aren't.
Of course the action of the waterstone breaking down as you use it changes it's cutting characteristics also. I don't have enough experience to know much about this, but I do know that the slurry produced to supposed to polish finer on most stones than the initial stone itself. Something like the "green brick of joy" is a 2000 grit stone. But people say that if you develop enough mud with it, and work it enough, the mud will break down to much finer and can leave a finish that's much like a 5000 grit stone! That's pretty interesting to me.
Ceramic versus waterstones: The ceramics I have (Spyderco) work really well. They load up a bit, but they are also easy to clean. A waterstone will load less generally speaking. But the cut of the ceramic is very different. First you have the cut of the abrasive particles in the ceramic. Sal says these are "synthetic sapphires". So they're super hard and cut well. But it's more complex than that, because the ceramic binder that holds them together has it's own "grit" or ability to polish. What it really seems to do is burnish the metal. The sapphires cut and the ceramic burnishes. What you end up with is kind of a smoothed out metal, but it's done with a different action than other abrasives. It's more of a slick finish than a toothy one in my opinion. This could be good or bad depending on what you want.
Waterstones, on the other hand, are polishing with just their abrasives particles, which are Aluminum Oxide (same as an "india stone"), or Silicon Carbide (same as "Crystolon stones"). As far as I know, the binder doesn't play in. It certainly does NOT burnish the metal. So the finish is quite different.
Other things that attracted me *personally* to waterstones:
Cutting power, but without deep scratches. I've been told waterstones cut as fast as diamonds on most metal, but leave a finer finish. So far, on non-super steels, this seems to be true. On super steels, I'm not so sure.
Ability to "skip grits". Making a leap from 1000 to 6000 is totally common with waterstones and seems to work really well. That's a time saver. Again with super hard steels this seems to be less true, but I have very little experience so far.
Ability to bear down on the stones *some* and not damage them. I'm *always* thinking I'm going to strip the diamonds off of my DMT Diasharp plates. I know I've removed a postage stamp sized area from my coarse plate. Darn it. With the waterstones I can go a bit harder and just not worry about it.
Working wet is very pleasant to me. The feel of some of the stones with water on top is... it's an intangible, and I like it. Which plays into a very intangible point for me: The traditional aspect of it. In some tiny nerdy way, I feel connected to the past when using waterstones. I feel like, in some way, this is the way sharpening was meant to be done. Some of the finest cutting tools ever made were sharpened and polished this way by some of the finest makers in history. That's pretty cool to me.
I'm not sure how accurate all of this is, but it's what I think.
Brian.
:thumbup:
